In the recent years, there has been increased interest in the development of small-molecule organic electronic materials as alternatives to inorganic semiconductors, such as silicon-based semiconductors, as they are lightweight, provide a high flexibility and allow manufacturing and processing of electronic devices at relatively low costs. Typically applied within thin films, such organic semiconductors find use in a large number of electronic devices, such as displays (including organic light-emitting diodes (OLED)), photovoltaics, and electronic circuits and components (e.g. organic field effect transistor (OFET) devices).
Ideally, organic semiconductors exhibit high charge carrier mobility or high field effect mobility, respectively, and favourable π-π stacking. Organic semiconductors fulfilling these criteria tend to be those which comprise compounds having a rigid planar structure and extensively conjugated π-systems allowing for the movement of electrons. In addition, it is of utmost importance that organic semiconductors are both highly soluble and thermally stable during solution processing.
Pentacene derivatives comprising trialkylsilylethynyl groups as solubilising groups, such as e.g. 6,13-bis[(triisopropylsilyl)ethynyl] pentacene (commonly referred to as “TIPS-pentacene”), have been widely used in view of their favourable solubility and stability in organic solvents as well as the performance in organic field effect transistors (see e.g. U.S. Pat. No. 6,690,029 B1).
In the recent years, efforts have been made to synthesize and investigate the charge carrier mobility performance of alternatives to TIPS-pentacene. To this end, the replacement of the pentacene core with other acene-based structures has been studied. Tang et al., Chem. Mater. 2008, 20(14), 4669-4676; Tang et al., J. Am. Chem. Soc. 2009, 131(14), 5264-5273; EP 1880 429 B1; US 2008/0191199 A1; and US 2009/0299070 A1 disclose that 5,12-bis(trialkylsilylethynyl)tetraceno[2,3-b]thiophenes represent promising candidates, particularly in view of their stable charge mobility when used in combination with organic binder materials, which are typically applied in order to improve the uniformity and integrity of organic thin films.
Palayangoda et al., J. Org. Chem. 2007, 72(17), 6584-6587 further disclose 5,12-bis(trialkylsilylethynyl)tetraceno[2,3-b]thiophenes bearing methoxy groups at the 6- and 13-positions of the tetraceno[2,3-b]thiophene core, which exhibit improved photooxidative stability.
However, since the hitherto disclosed compounds still leave room for improvements, it is desirable to provide alternative compounds that exhibit high field effect mobility, favourable π-π stacking, and at the same time show improved solubility and thermal stability during solution processing when compared to existing small-molecule organic semiconductors.